LLVMgold.so tests are duplicated in several places. Deduplicate them.
Move the tests to lto.c and lto.cu
Specify -fuse-ld=bfd or -fuse-ld=gold.
In a future change, if -fuse-ld=lld or CLANG_DEFAULT_LINKER=lld without -fuse-ld=, we will remove -plugin /path/to/LLVMgold.so
This fixes host-side LTO during CUDA compilation. Before, LTO
pipeline construction was clashing with CUDA pipeline construction.
At the moment there's no point doing LTO on device side as each
device-side TU is a complete program. We will need to figure out
compilation pipeline construction for the device-side LTO when we
have working support for multi-TU device-side CUDA compilation.
Differential Revision: https://reviews.llvm.org/D44691
llvm-svn: 328161